Determination of amino acids in feeds
1 Scope
This standard specifies the determination methods of total amino acids (peptide bonded and free) and free amino acids (natural and additive) in feeds, including conventional acid hydrolysis method, oxidative acid hydrolysis method, alkaline hydrolysis method and acid extraction method.
Conventional acid hydrolysis method is applicable to the determination of sulfur amino acids (cystine, cysteine and methionine) and amino acids other than tryptophan (aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, isoleucine, leucine, tyrosine, phenylalanine, lysine, histidine and arginine) in feedstuffs, formula feeds, concentrated feeds, concentrate supplements and additive premix feeds.
Oxidative acid hydrolysis method is applicable to the determination of sulfur amino acids (cystine, cysteine and methionine) in feedstuffs, formula feeds, concentrated feeds and concentrate supplements. If sodium metabisulfite is used as oxidation terminator, the protein hydrolytic amino acids other than tyrosine and tryptophan may be determined; if hydrobromic acid is used as terminator, the protein hydrolytic amino acids other than tyrosine, phenylalanine, histidine and tryptophan may be determined.
Alkaline hydrolysis method is applicable to the determination of tryptophan in feedstuffs, formula feeds, concentrated feeds and concentrate supplements.
Acid extraction method is applicable to the determination of free amino acids in formula feeds, concentrated feeds, concentrate supplements and additive premix feeds.
The limit of quantitation of each amino acid is shown in Table A.1 of Annex A.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated reference, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB/T 15399 Determination of sulfur amino acids in feeds - Ion exchange chromatography
GB/T 15400 Determination of tryptophan in feeds
GB/T 20195 Animal feeding stuffs - Preparation of test samples
JJG 1064 Automatic amino acid analyzer
3 Conventional acid hydrolysis method
3.1 Principle
The protein in feeds is hydrolyzed to amino acids under the action of 6mol/L hydrochloric acid solution at 110℃, separated by ion exchange chromatography and derivated by ninhydrin post-column. Proline is determined at a wavelength of 440nm and other amino acids are determined at a wavelength of 570nm.
3.2 Reagents or materials
Unless otherwise specified, analytically-pure reagents shall be adopted.
3.2.1 Water: complying with the requirements for Class-I water defined in GB/T 6682.
3.2.2 Hydrochloric acid: guaranteed reagent.
3.2.3 Hydrochloric acid hydrolysis solution (6mol/L): mix 500mL hydrochloric acid (3.2.2) with 500mL water, add 1g phenol and mix well.
Foreword i
1 Scope
2 Normative references
3 Conventional acid hydrolysis method
4 Oxidative acid hydrolysis method
5 Alkaline hydrolysis method
6 Acid extraction method
Annex A (Normative) Molar mass and limit of quantification of various amino acids
Annex B (Informative) Chromatograms of amino acid standard solution
